Encyclopdia Britannica Volume XIV Slice VII Ireland to Isabey Jean Baptiste

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Title: Encyclopaedia Britannica, 11th Edition, Volume 14, Slice 7
"Ireland" to "Isabey, Jean Baptiste"

Author: Various

Release Date: May 23, 2012 [EBook #39775]

Language: English

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THE ENCYCLOPÆDIA BRITANNICA

A DICTIONARY OF ARTS, SCIENCES, LITERATURE AND GENERAL

INFORMATION

ELEVENTH EDITION

VOLUME XIV SLICE VII

Ireland to Isabey, Jean Baptiste

Articles in This Slice

IRELAND
IRONWOOD

IRELAND, CHURCH OF
IRON-WOOD

IRENAEUS
IRONY

IRENE
IROQUOIS

IRETON, HENRY
IRRAWADDY

IRIARTE Y OROPESA, TOMÁS DE
IRREDENTISTS

IRIDACEAE
IRRIGATION

IRIDIUM
IRULAS

IRIGA
IRUN

Coasts.

IRIS (Greek mythology)
IRVINE

IRIS (botany)
IRVING, EDWARD

IRISH MOSS
IRVING, SIR HENRY

IRKUTSK (government of Russia)
IRVING, WASHINGTON

IRKUTSK (Russian town)
IRVINGTON

IRMIN
ISAAC (child of Abraham)

IRNERIUS
ISAAC I.

IRON
ISAAC II.

IRON AGE
ISAAC OF ANTIOCH

IRON AND STEEL
ISABELLA (queen of Castile)

IRON MASK
ISABELLA II.

IRON MOUNTAIN
ISABELLA (wife of Charles VI)

IRONSIDES
ISABELLA OF HAINAUT

IRONTON
ISABEY, JEAN BAPTISTE

IRELAND, an island lying west of Great Britain, and forming with it the United Kingdom of Great Britain and Ireland. It extends from

51° 26′ to 55° 21′ N., and from 5° 25′ to 10° 30′ W. It is encircled by the Atlantic Ocean, and on the east is separated from Great Britain
by narrow shallow seas, towards the north by the North Channel, the width of which at the narrowest part between the Mull of Cantire
(Scotland) and Torr Head is only 13½ m.; in the centre by the Irish Sea, 130 m. in width, and in the south by St George’s Channel, which
has a width of 69 m. between Dublin and Holyhead (Wales) and of 47 m. at its southern extremity. The island has the form of an irregular
rhomboid, the largest diagonal of which, from Torr Head in the north-east to Mizen Head in the south-west, measures 302 m. The greatest
breadth due east and west is 174 m., from Dundrum Bay to Annagh Head, county Mayo; and the average breadth is about 110 m. The
total area is 32,531 sq. m.

Ireland is divided territorially into four provinces and thirty-two counties:—(a) Ulster (northern division): Counties Antrim, Armagh,

Cavan, Donegal, Down, Fermanagh, Londonderry, Monaghan, Tyrone. (b) Leinster (eastern midlands and south-east): Counties Carlow,
Dublin, Kildare, Kilkenny, King’s County, Longford, Louth, Meath, Queen’s County, Westmeath, Wexford, Wicklow. (c) Connaught
(western midlands): Counties Galway, Leitrim, Mayo, Roscommon, Sligo. (d) Munster (south-western division): Counties Clare, Cork,
Kerry, Limerick, Tipperary, Waterford.

Physical Geography.—Ireland stands on the edge of the European “continental shelf.” Off the peninsula of Mullet (county Mayo) there

are 100 fathoms of water within 25 m. of the coast which overlooks the Atlantic; eastward, northward and southward, in the narrow seas,
this depth is never reached. The average height of the island is about 400 ft., but the distribution of height is by no means equal. The island
has no spinal range or dominating mountain mass. Instead, a series of small, isolated clusters of mountains, reaching from the coast to an
extreme distance of some 70 m. inland, almost surrounds a great central plain which seldom exceeds 250 ft. in elevation. A physical
description of Ireland, therefore, falls naturally under three heads—the coasts, the mountain rim and the central plain.

The capital city and port of Dublin lies a little south of the central point of the eastern coast, at the head of a bay which marks a

sudden change in the coastal formation. Southward from its northern horn, the rocky headland of Howth, the coast is generally steep,

occasionally sheer, and the mountains of county Wicklow approach it closely. Northward (the direction first to
be followed) it is low, sandy and fringed with shoals, for here is one point at which the central plain extends to
the coast. This condition obtains from 53° 25′ N. until at 54° N. the mountains close down again, and the

narrow inlet or fjord of Carlingford Lough separates the abrupt heights of the Carlingford and Mourne Mountains. Then the low and
sandy character is resumed; the fine eastward sweep of Dundrum Bay is passed, the coast turns north again, and a narrow channel
gives entry to the island-studded lagoon of Strangford Lough. Reaching county Antrim, green wooded hills plunge directly into the
sea; the deep Belfast Lough strikes some 10 m. inland, and these conditions obtain nearly to Fair Head, the north-eastern extremity of
the island. Here the coast turns westward, changing suddenly to sheer cliffs, where the basaltic formation intrudes its strange regular
columns, most finely developed in the famous Giant’s Causeway.

The low land surrounding the plain-track of the Bann intervenes between this and the beginning of a coastal formation which is

common to the north-western and western coasts. From the oval indentation of Lough Foyle a bluff coast trends north-westward to
Malin Head, the northernmost promontory of the island. Thence over the whole southward stretch to Mizen Head in county Cork is
found that physical appearance of a cliff-bound coast fretted with deep fjord-like inlets and fringed with many islands, which
throughout the world is almost wholly confined to western seaboards. Mountains impinge upon the sea almost over the whole length,
sometimes, as in Slieve League (county Donegal), immediately facing it with huge cliffs. Eight dominant inlets appear. Lough Foyle is
divided from Lough Swilly by the diamond-shaped peninsula of Inishowen. Following the coast southward, Donegal Bay is divided
from Galway Bay by the hammer-like projection of county Mayo and Connemara, the square inlet of Clew Bay intervening. At
Galway Bay the mountain barrier is broken, where the great central plain strikes down to the sea as it does on the east coast north of
Dublin. After the stern coast of county Clare there follow the estuary of the great river Shannon, and then three large inlets striking
deep into the mountains of Kerry and Cork—Dingle Bay, Kenmare river and Bantry Bay, separating the prongs of the forklike south-
western projection of the island. The whole of this coast is wild and beautiful, and may be compared with the west coast of Scotland
and even that of Norway, though it has a strong individuality distinct from either; and though for long little known to travellers, it now
possesses a number of small watering-places, and is in many parts accessible by railway. The islands though numerous are not as in
Scotland and Norway a dominant feature of the coast, being generally small and often mere clusters of reefs. Exceptions, however,
are Tory Island and North Aran off the Donegal coast, Achill and Clare off Mayo, the South Arans guarding Galway Bay, the
Blasquets and Valencia off the Kerry coast. On many of these desolate rocks, which could have afforded only the barest sustenance,
there are remains of the dwellings and churches of early religious settlers who sought solitude here. The settlements on Inishmurray

742

743

Mountains.

Central plain.

Rivers.

Lakes

(Sligo), Aranmore in the South Arans, and Scattery in the Shannon estuary, had a fame as retreats of piety and learning far outside
Ireland itself, and the significance of a pilgrimage to their sites is not yet wholly forgotten among the peasantry, while the preservation
of their remains has come to be a national trust.

The south coast strikes a mean between the east and the west. It is lower than the west though still bold in many places; the inlets

are narrower and less deep, but more easily accessible, as appears from the commercial importance of the harbours of Cork and
Waterford. Turning northward to the east of Waterford round Carnsore Point, the lagoon-like harbour of Wexford is passed, and then
a sweeping, almost unbroken, line continues to Dublin Bay. But this coast, though differing completely from the western, is not lacking
in beauty, for, like the Mournes in county Down, the mountains of Wicklow rise close to the sea, and sometimes directly from it.

Every mountain group in Ireland forms an individual mass, isolated by complex systems of valleys in all directions. They seldom

exceed 3000 ft. in height, yet generally possess a certain dignity, whether from their commanding position or
their bold outline. Every variety of form is seen, from steep flat-topped table-mountains as near Loughs Neagh
and Erne, to peaks such as those of the Twelve Pins or Bens of Connemara. Unlike the Scottish Highlands no

part of them was capable of sheltering a whole native race in opposition to the advance of civilization, though early customs, tradition
and the common use of the Erse language yet survive in some strength in the wilder parts of the west. From the coasts there is
almost everywhere easy access to the interior through the mountains by valley roads; and though the plain exists unbroken only in the
midlands, its ramifications among the hills are always easy to follow. Plain and lowland of an elevation below 500 ft. occupy nearly
four-fifths of the total area; and if the sea were to submerge these, four distinct archipelagos would appear, a northern, eastern,
western and south-western. The principal groups, with their highest points, are the Mournes (Slieve Donard, 2796 ft.) and the
Wicklow mountains (Lugnaquilla, 3039) on the east; the Sperrins (Sawel, 2240) in the north; the Derryveagh group in the north-west
(Errigal, 2466); the many groups or short ranges of Sligo, Mayo and Galway (reaching 1695 ft. in the Twelve Pins of Connemara); in
the south-west those of Kerry and Cork, where in Carrantuohill or Carntual (3414) the famous Macgillicuddy Reeks which beautify
the environs of Killarney include the highest point in the island; and north-east from these, the Galtees of Tipperary (3018) and Slieve
Bloom, the farthest inland of the important groups. Nearer the south coast are the Knockmealdown (2609) and Commeragh
Mountains (2470) of county Waterford.

It will be realized from the foregoing description that it is impossible to draw accurate boundary lines to the great Irish plain, yet it

rightly carries the epithet central because it distinctly divides the northern mountain groups from the southern.
The plain is closely correlated with the bogs which are the best known physical characteristic of Ireland, but
the centre of Ireland is not wholly bog-land. Rather the bogs of the plain are intersected by strips of low-lying

firm ground, and the central plain consists of these bright green expanses alternating with the brown of the bogs, of which the best
known and (with its offshoots) one of the most extensive is the Bog of Allen in the eastern midlands. But the bogs are not confined to
the plain. They may be divided into black and red according to the degree of moisture and the vegetable matter which formed them.
The black bogs are those of the plain and the deeper valleys, while the red, firmer and less damp, occur on the mountains. The former
supply most of the peat, and some of the tree-trunks dug out of them have been found so flexible from immersion that they might be
twisted into ropes. Owing to the quantity of tannin they contain, no harmful miasma exhales from the Irish bogs.

The central plain and its offshoots are drained by rivers to all the coasts, but chiefly eastward and westward, and the water-

partings in its midst are sometimes impossible to define. The main rivers, however, have generally a mountain
source, and according as they are fed from bogs or springs may be differentiated as black and bright streams.
In this connexion the frequent use of the name Blackwater is noticeable. The principal rivers are—from the

Wicklow Mountains, the Slaney, flowing S. to Wexford harbour, and the Liffey, flowing with a tortuous course N. and E. to Dublin
Bay; the Boyne, fed from the central plain and discharging into Drogheda Bay; from the mountains of county Down, the Lagan, to
Belfast Lough, and the Bann, draining the great Lough Neagh to the northern sea; the Foyle, a collection of streams from the
mountains of Tyrone and Donegal, flowing north to Lough Foyle. On the west the rivers are generally short and torrential, excepting
the Erne, which drains the two beautiful loughs of that name in county Fermanagh, and the Shannon, the chief river of Ireland, which,
rising in a mountain spring in county Cavan, follows a bow-shaped course to the south and south-west, and draws off the major part
of the waters of the plain by tributaries from the east. In the south, the Lee and the Blackwater intersect the mountains of Kerry and
Cork flowing east, and turn abruptly into estuaries opening south. Lastly, rising in the Slieve Bloom or neighbouring mountains, the
Suir, Nore and Barrow follow widely divergent courses to the south to unite in Waterford harbour.

The lakes (called loughs—pronounced lochs) of Ireland are innumerable, and (apart from their formation) are almost all contained

in two great regions, (1) The central plain by its nature abounds in loughs—dark, peat-stained pools with low
shores. The principal of these lie in county Westmeath, such as Loughs Ennel, Owel and Derravaragh, famed
for their trout-fishing in the May-fly season. (2) The Shannon, itself forming several large loughs, as Allen,

Ree and Derg; and the Erne, whose course lies almost wholly through loughs—Gowna, Oughter and the Loughs Erne, irregular of
outline and studded with islands—separate this region from the principal lake-region of Ireland, coincident with the province of
Connaught. In the north lie Loughs Melvin, close above Donegal Bay, and Gill near Sligo, Lough Gara, draining to the Shannon, and
Lough Conn near Ballina (county Mayo), and in the south, the great expanses of Loughs Mask and Corrib, joined by a subterranean
channel. To the west of these last, the mountains of Connemara and, to a more marked degree, the narrow plain of bog-land between
them and Galway Bay, are sown with small lakes, nearly every hollow of this wild district being filled with water. Apart from these
two regions the loughs of Ireland are few but noteworthy. In the south-west the lakes of Killarney are widely famed for their
exquisite scenic setting; in the north-east Lough Neagh has no such claim, but is the largest lake in the British Isles, while in the south-
east there are small loughs in some of the picturesque glens of county Wicklow.

Climate.—The climate of Ireland is more equable than that of Great Britain as regards both temperature and rainfall. No district in

Ireland has a rainfall so heavy as that of large portions of the Highlands of Scotland, or so light as that of several large districts in the east of
Great Britain. In January the mean temperature scarcely falls below 40° F. in any part of Ireland, whereas over the larger part of the
eastern slope of Great Britain it is some 3° lower; and in July the extremes in Ireland are 59° in the north and 62° in Kilkenny. The range
from north to south of Great Britain in the same month is some 10°, but the greater extent of latitude accounts only for a part of this
difference, which is mainly occasioned by the physical configuration of the surface of Ireland in its relations to the prevailing moist W.S.W.
winds. Ireland presents to these winds no unbroken mountain ridge running north and south, which would result in two climates as distinct
as those of the east and west of Ross-shire; but it presents instead only a series of isolated groups, with the result that it is only a few
limited districts which enjoy climates approaching in dryness the climates of the whole of the eastern side of Great Britain.

(O. J. R. H.)

Geology.—Ireland, rising from shallow seas on the margin of the submarine plateau of western Europe, records in its structure the

successive changes that the continent itself has undergone. The first broad view of the country shows us a basin-shaped island

744

consisting of a central limestone plain surrounded by mountains; but the diverse modes of origin of these mountains, and the
differences in their trend, suggest at once that they represent successive epochs of disturbance. The north-west highlands of Donegal
and the Ox Mountains, with their axes of folding running north-east and south-west, invite comparison with the great chain of
Leinster, but also with the Grampians and the backbone of Scandinavia. The ranges from Kerry to Waterford, on the other hand,
truncated by the sea at either end, are clearly parts of an east and west system, the continuation of which may be looked for in South
Wales and Belgium. The hills of the north-east are mainly the crests of lava-plateaux, which carry the mind towards Skye and the
volcanic province of the Faeroe Islands. The two most important points of contrast between the geology of Ireland and that of
England are, firstly, the great exposure of Carboniferous rocks in Ireland, Mesozoic strata being almost absent; and, secondly, the
presence of volcanic rocks in place of the marine Eocene of England.

The fact that no Cambrian strata have been established by palaeontological evidence in the west of Ireland has made it equally

difficult to establish any pre-Cambrian system. The great difference in character, however, between the Silurian strata at Pomeroy in
county Tyrone and the adjacent metamorphic series makes it highly probable that the latter masses are truly Archean. They form an
interesting and bleak moorland between Cookstown and Omagh, extending north-eastward into Slieve Gallion in county Londonderry,
and consist fundamentally of mica-schist and gneiss, affected by earth-pressures, and invaded by granite near Lough Fee. The axis
along which they have been elevated runs north-east and south-west, and on either flank a series of “green rocks” appears, consisting
of altered amygdaloidal andesitic lavas, intrusive dolerites, coarse gabbros and diorites, and at Beagh-beg and Creggan in central
Tyrone ancient rhyolitic tuffs. Red and grey cherts, which have not so far yielded undoubted organic remains occur in this series, and
it has in consequence been compared with the Arenig rocks of southern Scotland. The granite invades this “green-rock” series at
Slieve Gallion and elsewhere, but is itself pre-Devonian. Even if the volcanic and intrusive basic rocks prove to be Ordovician (Lower
Silurian), which is very doubtful, the metamorphic series of the core is clearly distinct, and appears to be “fundamental” so far as
Ireland is concerned.

The other metamorphic areas of the north present even greater difficulties, owing to the absence of any overlying strata older than

the Old Red Sandstone. Their rocks have been variously held to be Archean, Cambrian and Silurian, and their general trend has
undoubtedly been determined by post-Silurian earth-movements. Hence it is useful to speak of them merely as “Dalradian,” a
convenient term invented by Sir A. Geikie for the metamorphic series of the old kingdom of Dalriada. They come out as mica-schists
under the Carboniferous sandstones of northern Antrim, and disappear southward under the basaltic plateaux. The red gneisses near
Torr Head probably represent intrusive granite; and this small north-eastern exposure is representative of the Dalradian series which
covers so wide a field from central Londonderry to the coast of Donegal. The oldest rocks in this large area are a stratified series of
mica-schists, limestones and quartzites, with numerous intrusive sheets of diorite, the whole having been metamorphosed by pressure,
with frequent overfolding. Extensive subsequent metamorphism has been produced by the invasion of great masses of granite. Similar
rocks come up along the Ox Mountain axis, and occupy the wild west of Mayo and Connemara. The quartzites here form bare white
cones and ridges, notably in Errigal and Aghla Mt. in county Donegal, and in the group of the Twelve Bens in county Galway.

Following on these rocks of unknown but obviously high antiquity, we find fossiliferous Ordovician (Lower Silurian) strata near

Killary harbour on the west, graduating upwards into a complete Gotlandian (Upper Silurian) system. Massive conglomerates occur in
these series, which are unconformable on the Dalradian rocks of Connemara. In the Wenlock beds of the west of the Dingle
promontory there are contemporaneous tuffs and lavas. Here the Ludlow strata are followed by a thick series of barren beds (the
Dingle Beds), which have been variously claimed as Upper Silurian and Lower Devonian. No certain representative of the Dingle
Beds has been traced elsewhere throughout the south of Ireland, where the Old Red Sandstone succeeds the uptilted Silurian strata
with striking unconformity. The Silurian rocks were indeed greatly folded before the Old Red Sandstone was laid down, the general
trend of the folds being from south-west to north-east. The best example of these folds is the axis of Leinster, its core being occupied
by granite which is now exposed continuously for 70 m., forming a moorland from Dublin to New Ross. On either flank the Silurian
shales, slates and sandstones, which are very rarely fossiliferous, rise with steep dips. They are often contorted, and near the contact
with the granite pass into mica-schists and quartzites. The foothills and lowlands throughout southern Wicklow and almost the whole
of Wexford, and the corresponding country of western Wicklow and eastern Kildare, are thus formed of Silurian beds, in which
numerous contemporaneous and also intrusive igneous rocks are intercalated, striking like the chain N.E. and S.W. In south-eastern
Wexford, in northern Wicklow (from Ashford to Bray), and in the promontory of Howth on Dublin Bay, an apparently earlier series
of green and red slates and quartzites forms an important feature. The quartzites, like those of the Dalradian series, weather out in
cones, such as the two Sugarloaves south of Bray, or in knob-set ridges, such as the crest of Howth or Carrick Mt. in county
Wicklow. The radial or fan-shaped markings known as Oldhamia were first detected in this series, but are now known from
Cambrian beds in other countries; in default of other satisfactory fossils, the series of Bray and Howth has long been held to be
Cambrian.

All across Ireland, from the Ballyhoura Hills on the Cork border to the southern shore of Belfast Lough, slaty and sandy Silurian

beds appear in the axes of the anticlinal folds, surrounded by Old Red Sandstone scarps or Carboniferous Limestone lowlands. These
Silurian areas give rise to hummocky regions, where small hills abound, without much relation to the trend of the axis of elevation. The
most important area appears north of the town of Longford, and extends thence to the coast of Down. In Slieve Glah it reaches a
height of 1057 ft. above the sea. Granite is exposed along its axis from near Newry to Slieve Croob, and again appears at Crossdoney
in county Cavan. These occurrences of granite, with that of Leinster, in connexion with the folding of the Silurian strata, make it
highly probable that many of the granites of the Dalradian areas, which have a similar trend and which have invaded the schists so
intimately as to form with them a composite gneiss, date also from a post-Silurian epoch of earth-movement. Certain western and
northern granites are however older, since granite boulders occur in Silurian conglomerates derived from the Dalradian complex.

This group of N.E. and S.W. ridges and hollows, so conspicuous in the present conformation of Donegal, Sligo and Mayo, in the

axis of Newry, and in the yet bolder Leinster Chain, was impressed upon the Irish region at the close of Silurian times, and is clearly a
part of the “Caledonian” system of folds, which gave to Europe the guiding lines of the Scottish Highlands and of Scandinavia.

(Click to enlarge top section.)
(Click to enlarge bottom section.)

On the land-surface thus formed the Devonian lakes gathered, while the rivers poured into them enormous deposits of sand and

conglomerate. A large exposure of this Old Red Sandstone stretches from Enniskillen to the Silurian beds at Pomeroy, and some
contemporaneous andesites are included, reminding us of the volcanic activity at the same epoch in Scotland. The numerous
“felstone” dikes, often lamprophyric, occurring in the north and west of Ireland, are probably also of Devonian age. The
conglomerates appear at intervals through the limestone covering of central Ireland, and usually weather out as conspicuous scarps or
“hog’s-backs.” The Slieve Bloom Mountains are thus formed of a dome of Old Red Sandstone folded on a core of unconformable
Silurian strata; while in several cases the domes are worn through, leaving rings of Old Red Sandstone hills, scarping inwards towards
broad exposures of Silurian shales. The Old Red Sandstone is most fully manifest in the rocky or heather-clad ridges that run from the
west of Kerry to central Waterford, rising to 3414 ft. in Carrantuohill in Macgillicuddy’s Reeks, and 3015 ft. in Galtymore. In the
Dingle Promontory the conglomerates of this period rest with striking unconformity on the Dingle Beds and Upper Silurian series.
Here there may be a local break between Lower and Upper Devonian strata. The highest beds of Old Red Sandstone type pass up
conformably in the south of Ireland into the Lower Carboniferous, through the “Yellow Sandstone Series” and the “Coomhola Grits”

745

above it. The Yellow Sandstone contains Archanodon, the oldest known fresh-water mollusc, and plant-remains; the Coomhola Grits
are marine, and are sometimes regarded as Carboniferous, sometimes as uppermost Devonian.

In the south, the Carboniferous deposits open with the Carboniferous Slate, in the base of which the Coomhola Grits occur. Its

lower part represents the Lower Carboniferous Shales and Sandstones of the central and northern areas, while its upper part
corresponds with a portion of the Carboniferous Limestone. The Carboniferous Limestone, laid down in a sea which covered nearly
the whole Irish area, appears in the synclinal folds at Cork city and Kenmare, and is the prevalent rock from the north side of the
Knockmealdown Mountains to Enniskillen and Donegal Bay. On the east it spreads to Drogheda and Dublin, and on the west to the
heart of Mayo and of Clare. Loughs Mask and Corrib are thus bounded on the west by rugged Silurian and Dalradian highlands, and
on the east appear as mere water-filled hollows in the great limestone plain.

The Lower Carboniferous Sandstones are conspicuous in the region from Milltown near Inver Bay in southern Donegal to

Ballycastle in county Antrim. In the latter place they contain workable coal-seams. The Carboniferous Limestone often contains
black flint (chert), and at some horizons conglomerates occur, the pebbles being derived from the unconformable ridges of the
“Caledonian” land. A black and often shaly type called “calp” contains much clay derived from the same land-surface. While the
limestone has been mainly worn down to a lowland, it forms fine scarps and table-lands in county Sligo and other western regions.
Subterranean rivers and water-worn caves provide a special type of scenery below the surface. Contemporaneous volcanic action is
recorded by tuffs and lavas south-east of Limerick and north of Philipstown. The beds above the limestone are shales and sandstones,
sometimes reaching the true Coal-Measures, but rarely younger than the English Millstone Grit. They are well seen in the high ground
about Lough Allen, where the Shannon rises on them, round the Castlecomer and Killenaule coalfields, and in a broad area from the
north of Clare to Killarney. Some coals occur in the Millstone Grit horizons. The Upper Coal-Measures, as a rule, have been lost by
denudation, much of which occurred before Triassic times. South of the line between Galway and Dublin the coal is anthracitic, while
north of this line it is bituminous. The northern coalfields are the L. Carboniferous one at Ballycastle, the high outliers of Millstone Grit
and Coal-Measures round Lough Allen, and the Dungannon and Coalisland field in county Tyrone. The last named is in part
concealed by Triassic strata. The only important occurrences of coal in the south are in eastern Tipperary, near Killenaule, and in the
Leinster coalfield (counties Kilkenny and Carlow and Queen’s County), where there is a high synclinal field, including Lower and
Middle Coal-Measures, and resembling in structure the Forest of Dean area in England.

The “Hercynian” earth-movements, which so profoundly affected north-west and north-central Europe at the close of

Carboniferous times, gave rise to a series of east and west folds in the Irish region. The Upper Carboniferous beds were thus lifted
within easy reach of denuding forces, while the Old Red Sandstone, and the underlying “Caledonian” land-surface, were brought up
from below in the cores of domes and anticlines. In the south, even the Carboniferous Limestone has been so far removed that it is
found only in the floors of the synclinals. The effect of the structure of these folds on the courses of rivers in the south of Ireland is
discussed in the paragraphs dealing with the geology of county Cork. The present central plain itself may be regarded as a vast

shallow synclinal, including a multitude of smaller folds. The earth-wrinkles of this epoch were turned into a north-easterly direction
by the pre-existing Leinster Chain, and the trend of the anticlinal from Limerick to the Slieve Bloom Mountains, and that of the
synclinal of Millstone Grit and Coal-Measures from Cashel through the Leinster coalfield, bear witness to the resistance of this
granite mass. The Triassic beds rest on the various Carboniferous series in turn, indicating, as in England, the amount of denudation
that followed on the uplift of the Hercynian land. Little encouragement can therefore be given in Ireland to the popular belief in vast
hidden coalfields.

The Permian sea has left traces at Holywood on Belfast Lough and near Stewartstown in county Tyrone. Certain conglomeratic

beds on which Armagh is built are also believed to be of Permian age. The Triassic sandstones and marls, with marine Rhaetic beds
above, are preserved mainly round the basaltic plateaus of the north-east, and extend for some distance into county Down. An
elongated outlier south of Carrickmacross indicates their former presence over a much wider area. Rock-salt occurs in these beds
north of Carrickfergus.

The Jurassic system is represented in Ireland by the Lower Lias alone, and it is probable that no marine beds higher than the Upper

Lias were deposited during this period. From Permian times onward, in fact, the Irish area lay on the western margin of the seas that
played so large a part in determining the geology of Europe. The Lower Lias appears at intervals under the scarp of the basaltic
plateaus, and contributes, as in Dorsetshire and Devonshire, to the formation of landslips along the coast. The alteration of the
fossiliferous Lias by dolerite at Portrush into a flinty rock that looked like basalt served at one time as a prop for the “Neptunist”
theory of the origin of igneous rocks. Denudation, consequent on the renewed uplift of the country, affected the Jurassic beds until the
middle of Cretaceous times. The sea then returned, in the north-east at any rate, and the first Cretaceous deposits indicate the
nearness of a shore-line. Dark “green-sands,” very rich in glauconite, are followed by yellow sandstones with some flint. These two
stages represent the Upper Greensand, or the sandy type of the English Gault. Further sands represent the Cenomanian. The
Turonian is also sandy, but in most areas was not deposited, or has been denuded away during a local uplift that preceded Senonian
times. The Senonian limestone itself, which rests in the extreme north on Trias or even on the schists, is often conglomeratic and
glauconitic at the base, the pebbles being worn from the old metamorphic series. The term “Hibernian Greensand” was used by Tate
for all the beds below the Senonian; the quarrymen know the conglomeratic Senonian as “Mulatto-stone.” The Senonian chalk, or
“White Limestone,” is hard, with numerous bands of flint, and suffered from denudation in early Eocene times. Probably its original
thickness was not more than 150 ft., while now only from 40 to 100 ft. remain. This chalk appears to underlie nearly the whole
basaltic plateaus, appearing as a fringe round them, and also in an inlier at Templepatrick. The western limit was probably found in the
edge of the old continental land in Donegal. Chalk flints occur frequently in the surface-deposits of the south of Ireland, associated
with rocks brought from the north during the glacial epoch, and probably also of northern origin. It is just possible, however, that here
and there the Cretaceous sea that spread over Devonshire may have penetrated the Irish area.

After the Irish chalk had been worn into rolling downs, on which flint-gravels gathered, the great epoch of volcanic activity opened,

which was destined to change the character of the whole north-west European area. The critical time had arrived when the sea was
to be driven away eastward, while the immense ridges due to the “Alpine” movements were about to emerge as the backbones of
new continental lands. Fissure after fissure, running with remarkable constancy N.W. and S.E., broke through the region now
occupied by the British Isles, and basalt was pressed up along these cracks, forming thousands of dikes, from the coast of Down to
the Dalradian ridges of Donegal. One of these on the north side of Lough Erne is 15 m. long. The more deep-seated type of these
rocks is seen in the olivine-gabbro mass of Carlingford Mountain; but most of the igneous region became covered with sheets of
basaltic lava, which filled up the hollows of the downs, baked the gravels into a layer of red flints, and built up, pile upon pile, the great
plateaus of the north. There was little explosive action, and few of the volcanic vents can now be traced. After a time, a quiet interval
allowed of the formation of lakes, in which red iron-ores were laid down. The plant-remains associated with these beds form the only
clue to the post-Cretaceous period in which the volcanic epoch opened, and they have been placed by Mr Starkie Gardner in recent
years as early Eocene. During this time of comparative rest, rhyolites were extruded locally in county Antrim; and there is very strong
evidence that the granite of the Mourne Mountains, and that which cuts the Carlingford gabbro, were added at the same time to the
crust. The basalt again broke out, through dikes that cut even the Mourne granite, and some of the best-known columnar masses of
lava overlie the red deposits of iron-ore and mark this second basaltic epoch. The volcanic plateaus clearly at one time extended far
west and south of their present limits, and the denudation of the lava-flows has allowed a large area of Mesozoic strata also to
disappear.

Volcanic activity may have extended into Miocene times; but the only fossiliferous relics of Cainozoic periods later than the Eocene

are the pale clays and silicified lignites on the south shore of Lough Neagh, and the shelly gravels of pre-glacial age in county
Wexford. Both these deposits may be Pliocene. Probably before this period the movements of subsidence had set in which faulted the
basalt plateaus, lowered them to form the basin of Lough Neagh, and broke up the continuity of the volcanic land of the North
Atlantic area. As the Atlantic spread into the valleys on the west of Ireland, forming the well-known marine inlets, Europe grew,
under the influence of the “Alpine” movements, upon the east; and Ireland was caught in, as it were, on the western edge of the new
continent. It seems likely that it was separated from the British region shortly before the glacial epoch, and that some of the ice which
then abutted on the country travelled across shallow seas. The glacial deposits profoundly modified the surface of the country,
whether they resulted from the melting of the ice-sheets of the time of maximum glaciation, or from the movements of local glaciers.
Boulder-clays and sands, and gravels rearranged by water, occur throughout the lowlands; while the eskers or “green hills,”
characteristic grass-covered ridges of gravel, rise from the great plain, or run athwart valleys and over hill-sides, marking the courses
of sub-glacial streams. When the superficial deposits are removed, the underlying rocks are found to be scored and smoothed by ice-
action, and whole mountain-sides in the south and west have been similarly moulded during the Glacial epoch. In numerous cases,
lakelets have gathered under rocky cirques behind the terminal moraines of the last surviving glaciers.

There is no doubt that at this epoch various movements of elevation and subsidence affected the north-west of Europe, and modern

Ireland may have had extensions into warmer regions on the west and south, while the area now left to us was almost buried under
ice. In post-Glacial times, a subsidence admitted the sea into the Lagan valley and across the eastern shore in several places; but
elevation, in the days of early human occupation, brought these last marine deposits to light, and raised the beaches and shore-
terraces some 10 to 20 ft. along the coast. At Larne, Greenore and in the neck between Howth and Dublin, these raised beaches
remain conspicuous. To sum up, then, while the main structural features of Ireland were impressed upon her before the opening of
the Mesozoic era, her present outline and superficial contours date from an epoch of climatic and geographical change which falls
within the human period.

See maps and explanatory memoirs of the Geological Survey of Ireland (Dublin); G. Wilkinson, Practical Geology and Ancient

Architecture of Ireland (London, 1845); R. Kane, Industrial Resources of Ireland (2nd ed., Dublin, 1845); G. H. Kinahan,
Manual of the Geology of Ireland (London, 1878); E. Hull, Physical Geology and Geography of Ireland (2nd ed., London,

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1891); G. H. Kinahan, Economic Geology of Ireland (Dublin, 1889); A. McHenry and W. W. Watts, Guide to the Collection of
Rocks and Fossils, Geol. Survey of Ireland (2nd ed., Dublin, 1898).

(G. A. J. C.)

Economics and Administration

Population.—Various computations are in existence of the population of Ireland prior to 1821, in which year the first government

census was taken. According to Sir William Petty the number of inhabitants in 1672 was 1,320,000. About a century later the tax-
collectors estimated the population at a little over 2,500,000, and in 1791 the same officials calculated that the number had risen to over
4,200,000. The census commissioners returned the population in 1821 as 6,801,827, in 1831 as 7,767,401, and in 1841 as 8,196,597. It
is undoubted that a great increase of population set in towards the close of the 18th century and continued during the first 40 years or so of
the 19th. This increase was due to a variety of causes—the improvement in the political condition of the country, the creation of leaseholds
after the abolition of the 40s. franchise, the productiveness and easy cultivation of the potato, the high prices during the war with France,
and probably not least to the natural prolificness of the Irish people. But the census returns of 1851 showed a remarkable alteration—a
decrease during the previous decade of over 1,500,000—and since that date, as the following table shows, the continuous decrease in the
number of its inhabitants has been the striking feature in the vital statistics of Ireland.

Decrease per cent. of Population 1841-1901.

1841-1851.
1851-1861.
1861-1871.
1871-1881.
1881-1891.
1891-1901.

Leinster
15.25
12.86
8.11
4.49
6.8
3.5

Munster
22.47
18.53
7.93
4.98
11.8
8.4

Ulster
15.69
4.85
4.23
5.11
7.07
2.4

Connaught
28.81
9.59
7.33
3.43
12.4
9.7

Ireland
19.85
11.50
6.67
4.69
9.08
5.3

The cause of the continuous though varying decrease which these figures reveal has been emigration. This movement of population took

its first great impulse from the famine of 1846 and has continued ever since. When that disaster fell upon the country it found a teeming
population fiercely competing for a very narrow margin of subsistence; and so widespread and devastating were its effects that between
1847 and 1852 over 1,200,000 of the Irish people emigrated to other lands. More than 1,000,000 of these went to the United States of
America, and to that country the main stream has ever since been directed. Between 1851 and 1905 4,028,589 emigrants left Ireland—
2,092,154 males and 1,936,435 females, the proportion of females to males being extraordinarily high as compared with the emigration
statistics of other countries. Between these years the numbers fluctuated widely—1852 showing the highest total, 190,322 souls, and 1905
the lowest, 30,676 souls. Since 1892, however, the emigrants in any one year have never exceeded 50,000, probably because the
process of exhaustion has been so long in operation. As Ireland is mainly an agricultural country the loss of population has been most
marked in the rural districts. The urban population, indeed, has for some years shown a tendency to increase. Thus in 1841 the rural
population was returned as 7,052,923 and the urban as 1,143,674, while the corresponding figures in 1901 were respectively 3,073,846
and 1,384,929. This is further borne out by the percentages given in the above table, from which it will be seen that the greatest
proportional decrease of population has occurred in the two provinces of Munster and Connaught, which may be regarded as almost
purely agricultural. That the United States remained the great centre of attraction for Irish emigrants is proved by the returns for 1905,
which show that nearly 80% of the whole number for the year sailed for that country. Ireland does little to swell the rising tide of emigration
that now flows from England and Scotland to British North America.

Turning now to the census figures of 1901, we find that the population had diminished as compared with 1891 by 245,975. During the

decade only three counties, Dublin, Down and Antrim, showed any increase, the increase being due to the growth of certain urban areas.
Of the total population of 4,458,775, 2,200,040 were males and 2,258,735 were females. The inhabitants of the rural districts
(3,073,846) decreased during the decade by over 380,000; that of the urban districts, i.e. of all towns of not less than 2000 inhabitants
(1,384,929) increased by over 140,000. This increase was mainly due to the growth of a few of the larger towns, notably of Belfast, the
chief industrial centre of Ireland. Between 1891 and 1901 Belfast increased from 273,079 to 349,180; Dublin from 268,587 to 289,108;
and Londonderry, another industrial centre in Ulster, from 33,200 to 39,873. On the other hand, towns like Cork (75,978), Waterford
(26,743) and Limerick (38,085), remained almost stationary during the ten years, but the urban districts of Pembroke and of Rathmines
and Rathgar, which are practically suburbs of Dublin, showed considerable increases.

From the returns of occupation in 1901, it appears that the indefinite or non-productive class accounted for about 55% of the entire

population. The next largest class was the agricultural, which numbered 876,062, a decrease of about 40,000 as compared with 1891.
The industrial class fell from 656,410 to 639,413, but this represented a slight increase in the percentage of the population. The
professional class was 131,035, the domestic 219,418, and the commercial had risen from 83,173 in 1891 to 97,889 in 1901. The
following table shows the number of births and deaths registered in Ireland during the five years 1901-1905.

Births.
Deaths.

1901
100,976
79,119

1902
101,863
77,676

1903
101,831
77,358

1904
103,811
79,513

1905
102,832
75,071

The number of illegitimate births is always very small in proportion to the legitimate. In 1905 illegitimate births numbered 2710 or 2.6
of the whole, a percentage which has been very constant for a number of years.

Railways.—The first act of parliament authorizing a railway in Ireland was passed in 1831. The railway was to run from Dublin to

Kingstown, a distance of about 6 m., and was opened in 1834. In 1836 the Ulster railway to connect Belfast and Armagh, and the Dublin
and Drogheda railway uniting these two towns were sanctioned. In the same year commissioners were nominated by the crown to inquire

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(inter alia) as to a general system for railways in Ireland, and as to the best mode of directing the development of the means of intercourse
to the channels whereby the greatest advantage might be obtained by the smallest outlay. The commissioners presented a very valuable
report in 1838, but its specific recommendations were never adopted by the government, though they ultimately proved of service to the
directors of private enterprises. Railway development in Ireland progressed at first very slowly and by 1845 only some 65 m. of railway
were open. During the next ten years, however, there was a considerable advance, and in 1855 the Irish railways extended to almost 1000
m. The total authorized capital of all Irish railways, exclusive of light railways, at the end of 1905 was £42,881,201, and the paid-up
capital, including loans and debenture stock, amounted to £37,238,888. The total gross receipts from all sources of traffic in 1905 were
£4,043,368, of which £2,104,108 was derived from passenger traffic and £1,798,520 from goods traffic. The total number of passengers
carried (exclusive of season and periodical ticket-holders) was 27,950,150. Under the various acts passed to facilitate the construction of
light railways in backward districts some 15 lines have been built, principally in the western part of the island from Donegal to Kerry.
These railways are worked by existing companies.

The following table shows the principal Irish railways, their mileage and the districts which they serve.

Name of Railway.
Mileage.
Districts Served.

Great Southern & Western
1083
The southern half of Leinster, the whole of Munster, and part of

Connaught, the principal towns served being Dublin, Cork,
Waterford, Limerick and Sligo.

Midland Great Western
538
The central districts of Ireland and a great part of Connaught, the

principal towns served being Dublin, Athlone, Galway and Sligo.

Great Northern
533
The northern half of Leinster and a great part of Ulster, the principal

towns served being Dublin, Belfast, Londonderry, Dundalk,
Drogheda, Armagh and Lisburn.

Northern Counties (now

owned by the Midland
Railway of England)

249
The counties of Antrim, Tyrone and Londonderry.

Dublin & South Eastern
161
The counties of Dublin, Wicklow, Wexford and Waterford.

Donegal
106
The counties of Tyrone and Donegal.

Londonderry & Lough Swilly
99
The counties of Londonderry and Donegal.

Cork, Bandon & South Coast
95
The counties of Cork and Kerry.

Belfast & County Down
76
The county of Down.

Formerly Belfast and Northern Counties.
Formerly Dublin, Wicklow and Wexford.

There is no lack of cross-channel services between Ireland and Great Britain. Belfast is connected by daily sailings with Glasgow,

Ardrossan, Liverpool, Feetwood, Barrow and Heysham Harbour, Dublin with Holyhead and Liverpool, Greenore (Co. Down) with
Holyhead, Larne (Co. Antrim) with Stranraer, Rosslare (Co. Wexford) with Fishguard and Kingstown (Co. Dublin) with Holyhead.

Navigable Waterways.—Ireland is intersected by a network of canals and waterways, which if efficiently managed and

developed would prove of immense service to the country by affording a cheap means for the carriage of goods, especially
agricultural produce. Two canals—the Grand and the Royal—connect Dublin with the Shannon; the former leading from the south of
Dublin to Shannon Harbour and thence on the other side of that river to Ballinasloe, with numerous branches; the latter from the north
side of Dublin to Cloondera on the Shannon, with a branch to Longford. The Barrow Navigation connects a branch of the Grand
canal with the tidal part of the river Barrow. In Ulster the Bann navigation connects Coleraine, by means of Lough Neagh, with the
Lagan navigation which serves Belfast; and the Ulster canal connects Lough Neagh with Lough Erne. The river Shannon is navigable
for a distance of 143 m. in a direct course and occupies almost a central position between the east and west coasts.

Agriculture.—Ireland possesses as a whole a soil which is naturally fertile and easily cultiv...